How to calculate bags of cement required per cubic meter for different strengths of concrete

In construction, one cubic meter is a convenient and common way to measure quantities of material especially concrete which translates to cement, sand and chippings. Hence, we may want to calculate the amount of cement in a cubic meter depending on the strength of the concrete mix we aim to achieve.

There are many different concrete mixes but we will take the most common ones…

1:4:8

1:3:6

1:2:4

The process below outlines how we can calculate the cement required per cubic meter:

1. Determine the strength of concrete you wish to calculate for.

2.Add all the numbers in the mix together e.g. For 1:3:6 mix, we add 1+3+6=10

3. There are some constants involved

• Weight=Volume* Density
• Density of cement = 1440kg/m3
• One bag of cement=50kg
• Wet volume of concrete=1mx1m= 1m3
• Dry volume of concrete= 1m3*1.54= 1.54m3

  Concrete is mixture of cement, fine aggregate, course aggregate and water. When water is poured in cement and aggregate mixture the volume of dry mixture is reduced to some extent.

  1. Percentage of voids due to fine aggregate = 20 %
  2. Percentage of voids due to course aggregate = 32 – 34 %
  3. Total void percentage = 52 – 54 %

  Therefore,

  Dry volume = Wet volume + 54 % (Wet volume)

  So, 1.54 is conversion factor of wet volume to dry volume of concrete.

  If you want a 1 cubic meter of wet concrete, it means you have to make a dry mix of about 52 to 54% extra volume(1.52 to 1.54). This extra dry volume will balance to 1 cubic meter after pouring water.

4. We calculate the weight of cement

• Weight of cement = fraction of cement in the mix *Dry volume of concrete*Density of cement
• eg. Weight of cement for 1:4:8 mix= 1/13*1.54*1440= 170.58 kg

5. We divide the weight of cement derived in item 4 above by the weight of one bag of cement (50kg)

 

Practical examples:

For 1:4:8 mix

1+4+8= 13

Weight=Volume* Density

Density of cement = 1440kg/m3

One bag of cement=50kg

Wet volume of concrete=1mx1m= 1m3

Dry volume of concrete= 1m3*1.54= 1.54m3

Weight of cement = 1/13*1.54*1440= 170.58 kg

Bags of cement=170.58/50= 3.4 bags

3.4 bags of cement per cubic meter required for 1:4:8 mix.

 

For 136 mix

1+3+6=10
Part of cement
1/10

Weight of cement = 1/10*1.54*1440= 221.76 kg
Bags of cement=221.76/50= 4.4 bags

For 124 mix

1+2+4=7

Part of cement
1/7

Weight of cement = 1/7*1.54m3*1440kg/m3= 316.8 kg
Bags of cement=316.8kg/50= 6.34 bags

So, there we have it. This method can be used to calculate cement required per cubic meter for other concrete mixes as well.

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